In particular, in the case of multiplexers-demultiplexers (or Omux) integrated for example into space instruments, and comprising specific waveguides commonly called manifolds, the temperature changes may be large. These manifolds, which typically are made of aluminium, the coefficient of thermal expansion (CTE) of which is equal to 23 ppm, the deformations induced by these temperature changes are such that phase shifts are introduced into the guided waves. These phase shifts result in malfunction of the equipment. For example, Omux channel mismatches may occur.
To correct this problem, several technologies have been developed. The first method consists in producing the waveguide and the manifold in a material having a coefficient of thermal expansion as low as possible. Materials such as Invar™ have a coefficient of thermal expansion that may be down to 0.5 ppm, giving them a very low deformability with respect to temperature changes. However, for practical reasons, notably because the waveguides are mounted in space equipment generally produced in lightweight materials, the coefficients of thermal expansion of which are high, such as aluminium for example, mechanical compensation solutions are sought, notably for operating with aluminium waveguides. This is because too large a difference between the coefficient of thermal expansion of the manifold and that of the complete equipment on which it is mounted induces large mechanical stresses. To reduce these stresses, it is necessary to even out the coefficients of thermal expansion.
Nowadays, it is known that the thermal expansion of a waveguide of rectangular cross section can be compensated for by applying a deformation on its short sides so as to ensure phase stability. One existing technology consists in deforming the waveguide by pressing or pulling on its short sides by means of spacer components that move along an axis orthogonal to the short sides of the waveguide.
However, these technologies generally require the use of very large plates made of Invar™ (or another material having a similar coefficient of thermal expansion) that are parallel to the long sides of the waveguide and keep them spaced apart. The presence of these plates increases the space taken up by the waveguide.
To alleviate this drawback, the invention proposes the use of actuators made of Invar™ or another material of low coefficient of thermal expansion which, under the effect of a temperature change, cause longitudinal off-axis ribs, cut from the body of the waveguide and integral therewith, to rotate, deforming the short sides of the waveguide.